Sternal Dehiscence Reconstruction Treatment & Management
- Author: Mark A Grevious, MD, FACS; Chief Editor: Jorge I de la Torre, MD, FACS more...
If the presence of mediastinitis and sternal disruption are established, the patient should be immediately prepared to go to the operating room for exploration and debridement. The patient should be hydrated and started on broad-spectrum antibiotics. Once cultured, antibiotic therapy can be tailored to the specific organism. This therapy is aimed at preventing septic complications during debridement.
The goal of debridement is to excise all nonviable tissue, foreign bodies, and eradicate the infection. Irrigation may also be used to clean wounds. Several studies examined delayed versus immediate closure. Whether closure is immediate or delayed, the timing of reconstruction should coincide with a clean wound, healthy tissue margins, and time of flap closure or rigid sternal fixation.
Open packing of the sternum is used prior to delayed closure of the sternum. This leads to repeated packing changes, which are painful for the patient and time-consuming. The development of vacuum-assisted closure (VAC) has led to a more conservative approach to the management of sternal wound dehiscence.
The VAC is a negative pressure dressing used for the management of chronic and complex wounds. The advantages of a negative pressure dressing are reduced bacterial load, increased local blood flow to ischemic areas, and accelerated granulation tissue formation. Patients also have a stable sternum and freedom of movement while the wound heals. Song et al showed that using the VAC results in shorter time from debridement to definitive reconstruction. VAC therapy can be used as a stand-alone therapy or as an adjunct to reconstructive surgery. Possible complications from VAC therapy include an increased risk of bleeding, potential damage to the underlying tissue, and, rarely, right ventricular rupture.
The principles of adequate wound debridement, treatment of infection, and closure of dead space still predominate as initial management decisions in treating sternal wounds. The use of VAC helps decrease wound dressing changes, promotes granulation tissue, allows for smaller wounds to heal with secondary intention, and decreases edema in the tissues, which may allow the possibility for sternal salvage with rigid fixation.
Specific methods are discussed below.
Flaps Used in Reconstructing Dehisced Wounds
Once debrided and clean wound margins are established, numerous flaps are available for reconstruction. Pedicled muscular and musculocutaneous flaps are most often used. If no pedicled flap is available, then free flaps are used. Generally, the pectoralis major and rectus abdominis are considered first-line flaps and the omentum is considered second-line.
Pectoralis major flap
The pectoralis flap is the most commonly used pedicle flap. One or both of the pectoralis major muscles may be used to close a defect. See the image below.
The pectoralis muscle is a type V Mathes-Nahai classification flap, it has 2 dominant vascular contributions. Thus, it is unaffected by the harvesting of the internal mammary arteries (IMA) for coronary bypass. The pectoralis flap can be transposed into the mediastinum based on the more commonly used thoracoacromial pedicle or as a turnover flap based on internal mammary perforators. This muscle usually is the first choice in flap selection because of its proximity and relative ease of harvest. If the IMA is preserved, the muscle, based on perforators lateral to the IMA, can be turned over to cover the inferior sternum. The upper two thirds can be advanced into the defect based on the thoracoacromial vessels. See the image below.
When both IMAs are sacrificed, rotation-advancement can be performed based on the thoracoacromial vessels. Furthermore, muscle detachment from insertions on the clavicle and medial humerus allows a wider arc of rotation. Wide undermining of skin flaps then allows wound closure. One major limitation of the pectoralis major, when used solely for flap coverage, is the limited extent to which it covers the inferior third of the sternotomy wound. In turn, this is the most common site for dehiscence after flap repair.
Rectus abdominis muscular and musculocutaneous flap
The rectus abdominis flap was also been advocated for use in coverage. The rectus abdominus muscle is described as a turnover flap based on the superior epigastric system. The rectus muscle is easily dissected and has a wide arc of rotation. It can cover the lower third of the sternum and reach to the sternal notch. In a 2007 study by Davison et al, the rectus muscle alone proved superior in coverage to the inferior sternum. See the image below.
Using the rectus muscle as a flap is considered risky if the ipsilateral IMA has been used for coronary artery bypass. If the IMA is sacrificed on one side of the sternum, the decision is often made to mobilize the contralateral rectus. However, if the eighth anterior intercostal perforator to the rectus is preserved, coverage of the sternal wound can be performed with sacrifice of bilateral IMAs, but this is not always reliable.
In some instances, the muscle can be tunneled under a skin bridge separating the sternum from the donor site; however, carrying the sternal incision to the pubis for exposure and ease of flap inset can avoid undue tension. The risk of abdominal weakness and hernia is a potential complication, but closure of the rectus sheath fascia in place with a double-layered closure likely diminishes this complication.
If both IMAs are sacrificed, a definitive method of closure is the use of free tissue transfer. In one case, a patient who had right breast cancer with postoperative radiation developed an ipsilateral radiation induced sarcoma of the right breast and chest wall. The initial plan was for reconstruction with a pedicled transverse rectus abdominis myocutaneous (TRAM) flap. During the tumor extirpation, both IMAs were transected. The end of the contralateral IMA was dissected and prepared distally, and the rectus muscle was harvested and microvascular reconstruction was employed to cover the defect. See the image below.
The great majority of sternal wound coverage, especially the anterior two thirds, is performed using the pectoralis major, with the occasional use of the rectus abdominus to cover larger lower sternal defects. Nahai et al have developed an algorithm for local flap selection based on whether the saphenous vein is used as a bypass conduit or the IMAs are used in bypass surgery. Furthermore, the rectus abdominus and pectoralis muscle flaps can be used simultaneously to cover the large complicated sternal wound with minimal morbidity.
The omental flap is now widely regarded as a secondary line of flap coverage. Its use has several pointed advantages and disadvantages. Advantages include the ability to cover irregular defects, resistance to infection because of its blood supply and rich lymphatic system, as well as the ability to fill large defects. Potential complications include herniation, wound infection, bowel injury, lack of structural strength, lack of the ability to include a cutaneous island, ventral hernia, and the spread of infection from the mediastinum to the abdominal cavity.
In patients with previous irradiation to the chest wall, careful flap selection is paramount. Radiation effects include interference with DNA repair mechanisms, damage to the microcirculation of flaps with endothelial cell injury, and progressive fibrosis of skin. This can lead to wound healing, wound dehiscence, or total flap failure. Thus, awareness of the radiation field and muscle groups involved can guide the surgeon to alternate flaps for sternal coverage. The omentum has been used effectively for many years in the management of sternal wound dehiscence. Its broad, pliable, fatty nature allows it to conform and seal off the deep recesses in large wounds. Its rich abundant source of lymphatics also aids in clearing infection. Determine considerations for use preoperatively. A careful patient history is necessary to uncover previous gastric or colon procedures.
The approach usually is via midline laparotomy, although an approach through a previous cholecystectomy scar (right subcostal) can be effective in smaller patients. The omentum can be cleared of adhesions that may be present from previous abdominal surgery. Its blood supply is based on the right or left gastroepiploic artery, and significant mobilization can be gained by dividing the short gastrics along the greater curvature of the stomach. See the image below.
The risk of seeding infection into the peritoneal cavity is not substantiated in the literature, although gastric outlet obstruction is associated with excessive cranial traction on the antrum of the stomach during mobilization and inset of the omentum flap. Numerous reports in the literature state the effectiveness of the omentum flap in sternal coverage.
Latissimus dorsi and external oblique flaps
These muscle flaps are more suitable for smaller defects and should be reserved as back-up flaps in the event of flap failure. If detached from its insertion, the latissimus dorsi, based on the thoracodorsal artery, can fan across the anterior chest and cover the mediastinum. Patients must be turned into a lateral decubitus position for the maturation of the flap. Similarly, the external oblique muscles, based on intercostal perforators, can be turned into small sternal defects for coverage. See the image below.
Each patient presents with individualized issues that must be taken into account in making the final flap selection. The surgeon's skill and experience in concordance with the literature guide proper methods of reconstruction.
Rigid Fixation of the Sternum
Using soft tissue flaps as the primary method for addressing sternotomy wounds does not address the issue of the bony sternum. Complications of solely using flaps include loss of chest wall stability, chronic pain, paradoxical chest wall motion, and pulmonary function decreases. Limiting motion between relative segments of bone expedites sternal union and primary osseous healing. Throughout the literature, sternal plating has been shown to alleviate musculoskeletal pain in those with chronic sternal nonunion. Several surgeons now use rigid fixation techniques to stabilize the sternum prior to flap advancement. Restoration of sternal integrity approximates 96-98%.[8, 9, 10, 11, 12, 20]
Sternal nonunion can be treated with removal of sternal wires and debridement of fibrous tissue and devitalized bone, followed by rewiring or sternal plate fixation. However, in-vitro studies have shown the superiority of rigid plate fixation vs wire fixation.
Newer plate fixation technology, with locking screws, enables primary bone healing and accelerates recovery of sternal wounds by allowing a tension-free repair followed by elevation of pectoralis muscle flaps for closure if needed. Rigid fixation of the sternum also allows for a more rapid physiologic recovery of chest mechanics and decreases the possible paradoxical chest motion that accompanies sternal dehiscence. Ciclioni et al report that only 1 out of 50 patients presented with pectoralis dehiscence following sternal plating.
Newer rigid sternal fixation systems consist of titanium unilock screws and thick reconstruction plates available in different lengths. The plates are made of 2 parts that are connected to each other by an emergency release pin. These plates can be placed transversely or longitudinally. Care is taken to protect the mediastinal structures from the drill, and accurate measurement of screw depth ensures stable fixation with the locking plate.
Recent studies have determined that titanium plate fixation is effective to stabilize complicated sternal dehiscence. Studies indicate that transverse plate fixation achieves total sternal stabilization. Voss et al examined differences in transverse vs longitudinal placement of the plates. They determined that transverse plate placement has a requirement for more invasive access and is associated with more complications including pain and limited mobility of the ribs. Therefore, longitudinal plate placement is easier to apply and associated with fewer complications.
However, a newer sternal clamp device called the Rapid Sternal Closure (RSC) Talon system (KLS-Martin, Germany) has been introduced. The RSC Talon is a transverse system that was recently approved by the US Food and Drug Administration (FDA) for rigid sternal fixation. In the short term, this system has shown to be reliable, but no studies have been performed to show long-term outcomes. Sternal plating concerns include the possibility of foreign body infection and necessary plate removal because of loosened or incorrectly placed hardware.
When significant osteomyelitis of the sternum has occurred, fixing the sternum is impossible. The persistent infection results in a recurring sinus tracts and infectious drainage unless the infected bone and hardware are removed. Limited resection often results in postoperative pain when the residual sternum rubs or clicks together. Radical resection of the sternum addresses this problem; patients rarely experience significant functional limitations after total sternectomy. If the manubrium is unaffected, it should be preserved and stabilized. Resected bone that appears grossly to have evidence of infection should be sent for cultures to ensure appropriate postoperative antibiotic coverage.
The operation usually begins with a thorough debridement of the skin, subcutaneous tissues, and bone of the mediastinal wound. See the images below.
Tissue should be sent for culture, as should routine swab cultures of purulent wounds. Bone should be sent to pathology to rule out osteomyelitis. Depending on the hemodynamic status of the patient, a radical debridement can be followed by immediate flap reconstruction or staged with daily wound care, treatment of infection, and stabilizing the patient prior to definitive wound closure.
Important considerations for successful closure of these wounds include tension-free muscle flap advancement and skin closure and the use of closed suction drains placed beneath both the muscle flaps and skin flaps. See the images below.
Drains are usually removed when output is less than 20 mL/d. Patients are cautioned against resistive exercises or activities that put stress on the suture line or central chest for at least 6 weeks.
Closure of flaps over drains is necessary to prevent seroma formation and subsequent wound healing problems. Complications of flap closure of sternal wounds include hematoma, dehiscence, and sternal necrosis with osteomyelitis. Hematoma formation can be prevented with careful attention to hemostasis, careful dissection of pedicles, and closure over suction drains. Place drains under the muscle/omentum flap, under skin flaps, and at large undermining or dissection sites. Dehiscence is observed in obese patients, older patients with chronic obstructive pulmonary disease (COPD), patients on prolonged ventilatory support, patients with sepsis, and in women with large pendulous breasts. In the latter, surgical bras and tapes are necessary to prevent distraction on the medial chest and separation of the flaps.
Sternal necrosis and osteomyelitis occur in patients with profound sepsis, with gram-positive infections, and on whom inadequate debridement is performed. Debridement is the cornerstone in healing these wounds; debride viable, bleeding bone. Some advocate resection of the entire sternum and costal cartilages to reduce the chance of recurrent infection. Regardless, perform bone biopsies at the farthest margin of debridement.
If dehiscence is observed early, 1-stage debridement followed by immediate flap transposition can be performed. However, if the wound is grossly purulent at initial debridement, performing wound care with dressing changes is a reasonable course of action. Further debridement may be necessary with quantitative cultures, assuring a noninfected wound prior to closure. Depending on the extent of infection, a course of intravenous antibiotics for 6 weeks may be necessary to eradicate the infection.
Future and Controversies
The management and treatment of mediastinitis and sternal wound dehiscence has progressed greatly in the past 50 years. Wound debridement, vascularized flap transposition, and rigid sternal stabilization greatly decrease the morbidity, mortality, and cost of treating this devastating complication of thoracic surgery. The addition of vacuum-assisted closure (VAC) devices and development of newer rigid plate technology add weapons in the armamentarium for the management of these complex wounds. Future developments for managing difficult wound problems undoubtedly will arise, allowing the specialty of plastic surgery to contribute to the well-being of patients.
A retrospective study by Tarzia et al found a lower rate of complications and mortality associated with VAC for sternal wound dehiscence than with conventional treatment for the condition. In the study, involving patients who suffered sternal wound dehiscence after cardiac surgery, there was no dehiscence-related mortality in patients treated with VAC, compared with 11% mortality in those who received conventional treatment. The VAC group also experienced a significantly lower incidence of mediastinitis, sepsis, delayed sternal wound dehiscence infection, and other complications. The rate of surgical sternal and superficial revisions was also significantly lower in these patients.
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